This section introduces aspects that may facilitate better understanding of the present disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
The fast uptake of the Third Generation Partnership Project (3GPP)-Long Term Evolution (LTE) in different regions of the world shows both that demand for wireless broadband data is increasing, and that LTE is a successful platform to meet that demand. The existing and new spectrum licensed for exclusive use by International Mobile Telecommunications (IMT) technologies will remain fundamental for providing seamless coverage, achieving the higher spectral efficiency, and ensuring the higher reliability of cellular networks through careful planning and deployment of high-quality network equipment and devices.
In order to meet the ever increasing data traffic demand from users, particularly in concentrated high traffic buildings or hot spots, more mobile broadband bandwidth will be needed. Given a large amount of spectrum available in unlicensed bands around the globe, the unlicensed spectrum is more and more considered by cellular operators as complementary means to augment their service offering. While the unlicensed spectrum may not match the qualities of the licensed regime, solutions that allow an efficient use of it as a complement to licensed deployments have a potential to bring a great value to 3GPP operators, and ultimately to the 3GPP industry as a whole. This type of solutions would enable operators and vendors to leverage the existing or planned investments in LTE/Evolved Package Core (EPC) hardware in radio and core networks.
It has been agreed to study Licensed-Assisted Access (LAA) technologies in the 3GPP at RP-141664. This LAA framework builds on carrier aggregation solutions introduced in LTE Release-10 to access the additional bandwidth in the unlicensed spectrum. FIG. 1 shows an illustrative LTE network that configures a user equipment, UE, to aggregate additional secondary cells (SCells) which are using frequency carriers in the unlicensed spectrum. The primary cell (PCell) maintains exchange of essential control messages and also offers an always-available robust spectrum, i.e. the licensed spectrum, for real-time and high-value traffic. Via the high-quality and robust licensed spectrum, the PCell may also provide mobility handling and management for the UE. The aggregated SCells in the unlicensed spectrum, when available, can be utilized as a bandwidth booster to serve, e.g. the best effort traffic. The LAA SCells may operate in a downlink (DL)-only mode or operate with both uplink (UL) and DL traffic.
However, in the existing LTE systems, control information and data are usually transmitted on licensed carriers only. There is no a solution adapted for LAA systems to leverage resources on both licensed and unlicensed carriers so as to further improve transmission performance.